Modular Installation for Treating Water by Flotation

Abstract

Installation for treating water by flotation, comprising a substantially parallelepipedal assembly (1) produced by connecting modules (2, 2a), said assembly comprising a contact tank (3) which is provided with supply means for water to be treated (4) and supply means for white water (5), a flotation tank (6) which is provided with means for discharging treated water (7, 7a) and which is separated from said contact tank by a vertical wall (8), and means for discharging floated sludge, characterised in that said contact tank (3) is provided along said flotation tank (6) and delimits a single contact zone for said water to be treated with said white water, and in that said supply means for water to be treated (4) are configured to distribute the water to be treated in said contact tank according to a longitudinal water supply flow, the water distribution flow in the flotation tank being perpendicular to said water supply flow in said contact tank.

Claims

1. Installation for treating water by flotation, comprising a substantially parallelepipedal assembly (1) produced by connecting modules (2, 2a), said assembly comprising a contact tank (3) which is provided with supply means for water to be treated (4) and supply means for white water (5), a flotation tank (6) which is provided with means for discharging treated water (7, 7a), said flotation tank (6) being separated from said contact tank by a vertical wall (8), and means for discharging floated sludge, characterised in that said contact tank (3) is provided along said flotation tank (6) and delimits a single contact zone for said water to be treated with said white water, and in that said supply means for water to be treated (4) are configured to distribute the water to be treated in said contact tank according to a longitudinal water supply flow, the water distribution flow in the flotation tank (A) being perpendicular to said water supply flow (B) in said contact tank.

2. Installation according to claim 1, characterised in that the height (H) of the flotation tank is comprised between 1 and 4 m, preferably between 1 and 2.5 m, and that the width (1) of the flotation tank is comprised between 0.5 and 4 m.

3. Installation according to claim 1 or 2, characterised in that said means for supplying white water in the contact tank include a multiphase pump associated with nozzles capable of producing bubbles of a very small diameter.

4. Installation according to claim 3, characterised in that said means for supplying white water in the contact tank include a multiphase pump and a static mixer associated with nozzles capable of producing bubbles of a very small diameter.

5. Installation according to claim 3 or 4, characterised in that said nozzles are provided at a height (h) from the bottom of said contact tank comprised between 0.2 and 2 metres.

6. Installation according to claim 5, characterised in that said nozzles are provided with a nozzle density comprised between 3 and 30 nozzles, preferably between 5 and 12 nozzles, per square metre of said contact tank bottom.

7. Installation according to any one of the preceding claims, characterised in that said assembly is produced by connecting 2 to 24, preferably 2 to 12, modules.

8. Installation according to any one of the preceding claims, characterised in that its total length (LT) is comprised between 0.5 and 20 m, preferably between 1 and 12 m.

9. Installation according to any one of the preceding claims, characterised in that said means for supplying water to be treated in said contact tank comprise a perforated pipe provided longitudinally in the lower part of said contact tank.

10. Installation according to any one of the preceding claims, characterised in that said means for discharging treated water comprise at least one perforated pipe provided longitudinally in the lower part of said flotation tank.

11. Installation according to any one of the preceding claims, characterised in that said means for discharging floating sludge comprise a scraper provided with means for moving along a longitudinal axis, transverse to the water distribution flow (A) in the flotation tank.

12. Installation according to any of the preceding claims, characterised in that the ratio between the height (H) and the width (L) of the flotation tank is greater than 1.1.

Description

LIST OF FIGURES

[0043] An embodiment, given merely as an example, of the flotation installation according to the present invention will now be described in detail, with reference to the drawings, wherein:

[0044] FIG. 1 is a perspective view of an embodiment of the present invention;

[0045] FIG. 2 shows a partially transparent perspective view of this embodiment;

[0046] FIG. 3 is a horizontal cross-section view P-P′ of the installation to clarify the water flows in its tanks;

[0047] FIG. 4 is a perspective view of one of the modules making up the assembly of contact and flotation tanks of this installation;

[0048] FIG. 5 is a schematic top view of the assembly of contact and flotation tanks of this installation;

[0049] FIG. 6 is a side cross-section view of the assembly of contact and flotation tanks of this installation;

[0050] FIG. 7 is a graph showing the removal of suspended matter from an effluent using a flotation installation of the prior art according to WO2008142026;

[0051] FIG. 8 is a graph showing the suspended matter contents at the input and output of a flotation installation according to the invention of the same effluent;

[0052] FIG. 9 is a photograph taken from above of the contact tank of the installation according to the invention described with reference to FIGS. 1 to 6 during the tests that led to producing the graph shown in FIG. 8.

EMBODIMENT OF AN INSTALLATION ACCORDING TO THE INVENTION

[0053] With reference to FIGS. 1 to 6, the installation shown comprises an assembly 1 of tanks having a parallelepipedal shape arranged on a frame 1a. In addition to this assembly 1, this frame 1a accommodates means for producing white water 10.

[0054] This assembly of tanks is produced by connecting two modules 2 as shown in FIG. 4. It will be noted that in other embodiments, more than two modules may of course be used to produce said assembly.

[0055] These modules 2 are connected to each other and associated with end walls 2a and 2b to form the assembly 1 according to techniques known to those skilled in the art and thus produce a contact tank 3 and a flotation tank 6.

[0056] The contact tank 3 is provided with supply means for water to be treated 4 and supply means for white water 5.

[0057] The supply means for water to be treated 4 include a perforated pipe provided in the lower part of the contact tank 3, longitudinally to it.

[0058] The supply means for white water 5 include a supply pipe provided with nozzles 5a (see FIG. 6) allowing the generation of air bubbles with a very small diameter and connected to a multiphase pump (not shown).

[0059] This pipe is provided parallel to the pipe of the supply means for water to be treated 4, and above it. As can be seen in FIG. 6, these nozzles are thus provided in the contact tank at a height (h) from the bottom 3a of the latter, comprised between 0.2 and 2 metres. The nozzle density on the pipe is designed to optimise the flotation process in the flotation tank and is, in practice, advantageously comprised between 3 and 30 nozzles per square metre of contact tank bottom.

[0060] The flotation tank 6 is also provided with means for discharging treated water comprising two pipes 7, 7a provided in its lower part. The flotation tank 6 is separated from said contact tank by a vertical wall 8.

[0061] The flotation tank is also provided with means for discharging floating sludge comprising a weir 9 and a scraper 11 (shown in FIG. 5).

[0062] According to the invention, said contact tank 3 is provided along said flotation tank 6 and delimits a single contact zone for said water to be treated with said white water.

[0063] Also according to the invention, and with reference to FIG. 3, the supply means for water to be treated 4 are configured to distribute the water to be treated in the contact tank 3 according to a longitudinal water supply flow, the distribution flow (A) of water in the flotation tank 3 being perpendicular to the water supply flow (8) in the contact tank 6.

[0064] In operation, the water to be treated is supplied to the single flotation zone delimited by the flotation tank 3, through the pipe 4, where it is brought into contact with the white water supplied by the pipe 5 provided with nozzles.

[0065] The very fine air bubbles dispensed by these nozzles immediately mix with the water to be treated and this mixture overflows through the wall 8 into the flotation tank 6. In this tank 8, the flotation of the matter to be separated from the water takes place thanks to the action of the air bubbles which, by mixing with this matter, reduce its density and thus make it float,

[0066] Periodically, the scraper 11 is operated to push the floating matter to the surface of the water in the flotation tank and also in the contact tank to the weir 9, to be discharged from the installation for possible treatment. To this end, this scraper has a moving axis 11a perpendicular to the treatment flow A of the water in the flotation tank 6.

[0067] It will therefore be noted that the scraper 11 is designed to scrape both the surface of the water in the flotation tank 6 and the one in the contact tank 3. As a corollary, the weir 9 extends transversely to these two tanks in order to be able to receive the floated matter.

[0068] The treated water is collected in the lower part of the flotation tank through pipes 7 and 7a.

Comparative Tests

[0069] The flotation installation according to the invention described above and a flotation installation of the prior art according to WO2008142026 were implemented to treat an effluent consisting of water from a dairy industry.

[0070] In comparison, the installation according to the invention is much more compact than the tested installation of the prior art. In practice, this installation according to the invention has a size 30% smaller than the latter.

[0071] Moreover, compared to the installation of the prior art, the installation according to the invention is modular and can be transported in a container, whereas the one of the prior art system is neither modular nor transportable.

[0072] Different batches of said effluent were treated by the installation according to WO2008142026 and, for each batch, the suspended matter (MES) content at the input on the raw water and at the outlet of the installation on the clarified water was measured in order to deduce, for each batch, the abatement rate, expressed in %, of this matter.

[0073] During these tests, a coagulant and a flocculant were injected into the installation.

[0074] The tests were carried out with the effluent flowing through the installation at a mirror velocity of 26 m/h.

[0075] With reference to FIG. 7, varying abatement rates of suspended matter according to the batches were observed from 85% to 98%.

[0076] Different batches of the same effluent were then treated using the embodiment of the invention described with reference to FIGS. 1 to 6.

[0077] With reference to FIG. 8, for each batch, the suspended matter content (TSS) at the input and the output of the installation was measured. Based on these measurements, the abatement rates of suspended matter were calculated and found to be quite comparable to those obtained with the installation according to WO2008142026.

[0078] The tests were carried out with the effluent flowing through the installation at mirror velocities also similar to those implemented with the installation of the prior art, varying from 20 to 25 m/h depending on the batches.

[0079] These comparative tests show that the installation according to the invention offers treatment performances that are equivalent to those of the installation of the prior art while being 30% smaller in size.

[0080] This is due to the improved distribution of white water in the contact tank made possible by the invention. With reference to the photograph in FIG. 9, which shows a uniformly white colour of the mixture of effluent and white water present in the contact tank of the installation in FIGS. 1 to 6, the invention indeed allows to distribute the white water uniformly in the contact tank and thus to ensure that the entirety of the treated effluent is brought into contact with the same quantity of white water.